Shroud for fire-tube boiler

ABSTRACT

A device for controlling the circulation of liquid and vapor in a fire-tube boiler comprising a semicylindrical shroud disposed in closely spaced relationship to the liquid-receiving shell of the boiler. Heat transfer means located within the shell beneath the shroud vaporizes the liquid and conduit means directs vaporliquid mixture to a separation chamber disposed above the shell. Other conduit means returns condensed and unvaporized liquid to the area between the shroud and the boiler shell and the shroud directs this liquid to the bottom of the shell.

United States Patent Charles D. Freeman Kansas City Aug. 22, 1969 June 8, 1971 J. F. Pritchard and Company Kansas City,

inventor Applv No, Filed Patented Assignee Sl-IROUD FOR FIRE-TUBE BOILER 2 Claims, 3 Drawing Figs.

US. Cl

Int. Cl

Field of Search References Cited UNITED STATES PATENTS 9/1903 Auldjo 3,103,206 9/1963 Halvorsen et al. 122/34 3,123,053 3/1964 Webster et al..... 122/34 3,463,125 8/1969 Voorheis l22/406X Primary Examiner-Kenneth W, Sprigue AttorneySchmidt, Johnson, Hovey & Williams PATENTED JUN 8197i INVENTOR Charles D. Freeman ATTORNEYS.

SHROUD FOR FIRE-TUBE BOILER This invention relates to liquid heating apparatus and, more particularly, to a device for more effectively controlling the circulation of liquid and vapor in a liquid boiler than has been the case heretofore.

Many types of boilers and heaters are used in various industrial applications to vaporize liquids. One particular type of heater that is frequently employed to utilize the waste heat from a combustion reaction is the so-called fire-tube boiler wherein a plurality of elongated fire tubes are disposed in a shell that is filled with the liquid to be vaporized. A separation chamber that communicates with the boiler shell through appropriate conduit means is disposed above the shell and separates the liquid-vapor mixture, directing the vapor to a point of use and returning condensed and unvaporized liquid to the heating area for revaporization.

It has been the practice with such prior devices to provide appropriate conduit means that extend externally of both the separation chamber and the boiler shell to provide a path for the return of condensed and unvaporized liquid to the heating area.

A major difi'lculty with this construction is that with the conduit means exposed to the ambient air, the temperature differential between the air and the heated liquid creates a severe metal expansion problem. External insulation of the boiler assembly can be provided but this is expensive, time consuming, and adds to the bulkiness of the assembly while detracting from its neat appearance.

Another problem which has not been adequately solved is that with the liquid return conduits projecting externally of the separation chamber and the boiler shell, shipment of the boiler assembly is made extremely difficult. In some cases the liquid-retum conduits are manufactured as separate components and installed at the point of use by field welding. This is not satisfactory in view of the fact that the entire assembly is normally subjected to stress relief by the manufacturer at the time of fabrication and the field welding defeats the purpose of the stress relief. X-ray quality control of the weld joints is also not possible.

It is, therefore, an object of this invention to provide semicylindrical circulation control structure for a liquid boiler which functions to cause condensed and unvaporized liquid returned to the boiler shell from the separation chamber to be distributed over an area substantially equal to the inside area of the shell, thereby achieving superior distribution of this liquid.

A further object of the invention is to provide circulation control structure for a liquid boiler which is completely disposed within the boiler shell thereby eliminating the need for field welding.

A still further object of the invention is to provide a liquid boiler assembly wherein external insulation of the boiler is simplified by avoiding the provision of external conduits.

Another very important object of the invention is to provide circulation control structure for a liquid boiler wherein the condensed and unvaporized liquid is returned to the heating area through conduits of a relatively large diameter, thereby minimizing pressure drop through the conduit and enhancing circulation.

It is also an object of this invention to provide circulation control structure for a liquid boiler wherein the difference between the density of liquid plus vapor and condensed and unvaporized liquid is utilized most effectively to achieve circulation within the boiler by distributing the condensed and unvaporized liquid over an area substantially equal to the inside area of the boiler shell.

Other objects of the invention will be made clear or become apparent from the following description of a preferred embodiment.

Referring to the drawing:

FIG. 1 is a front elevational view of a boiler shell and its associated separation chamber illustrating the novel circulation control shroud of this invention in its preferred disposition,

portions of the shell and the separation chamber being broken away for purposes of illustrations;

FIG. 2 is an enlarged, cross-sectional view of the boiler shell and separation chamber taken along line 2'-2 of FIG. 1; and

FIG. 3 is an enlarged, sectional view through the boiler shell illustrating the mounting assembly for the circulation-shroud.

Referring to FIGS. 1 and 2 wherein the number 10 generally designates a boiler assembly, the assembly 10 includes a cylindrical boiler shell 12, and a cylindrical separation chamber 14 disposed above the shell and connected thereto by a plurality of conduits 11. A plurality of horizontal fire tubes 16 are disposed within the shell 12 and extend substantially the entire length thereof as do a plurality of gas-retum tubes 18. Upright baffles 17 support tubes 16 and 18 and a pair of openings 19 serve as combustion gas outlets.

A shroud 20 is held within the shell 12 in closely spaced relationship thereto by a plurality of mounting brackets 22 at a distance approximately equal to the thickness of the shell 12. Each bracket 22 includes an inwardly projecting bolt 23 secured to the inner wall surface of shell 12 and provided with a washer 25 thereon. Shroud 20 has an opening therein receiving each bolt 23, and washer and nut assembly 27 holds the shroud 20 against a corresponding washer 25. The shroud 20 consists of a pair of arcuate sections 24 and 26 that extend around the boiler shell through a combined arc of approximately 270, and an elongated, planar member 28 joined to the upper opposed margins of sections 24 and 26. The member 28 connects the arcuate sections 24 and 26 respectively, to a plurality of conduits 32 that communicate the interior of the boiler shell 12 with the interior of the separation chamber 14. Each of the conduits 32 extends upwardly through a respective conduit 11 and is provided with a baffle 34 at the end thereof disposed within the separation chamber 14 for purposes to be made clear hereinafter.

The conduits 11 which are concentric with each of the first conduits 32 and are disposed in circumscribing spaced relationship to the latter, extend from the bottom of the separation chamber 14 to the top of the boiler shell 12 to communicate the separation chamber 14 with the area 38 between the boiler shell 12 and the shroud 20. The boiler shell 12 is normally filled with water or other liquid to substantially a level 40 within the separation chamber 14 through an inlet opening 42. A blowdown outlet 44 is provided in the bottom of the boiler shell 12 to permit periodic emptying of the assembly 10 under pressure to prevent the buildup of mineral deposits.

The separation chamber 14 includes a vapor outlet conduit 46 and a hemicircular dry-pipe 48 disposed at the top of the chamber 14. Pipe 48 is provided with a downspout 50.

ln operation, after the boiler shell 12 has been tilled with liquid to a level 40 and the flow of combustion gas has been initiated through the fire tubes 16 and return tubes 18, the liquid-vapor mixture, which has a density less than the density of the condensed and unvaporized liquid, begins to rise through the conduits 32 and the liquid-vapor mixture is directed into the separation chamber 14 by the baffles 34.

The vapor continues to rise in separation chamber 14, passes along the dry-pipe 48, and leaves the assembly 10 through outlet conduit 46. The dry-pipe 48 serves to prevent liquid droplets from contaminating the vapor, and any vapor that is condensed in the dry-pipe 48 is returned to the lower part of the separation chamber 14 through downspout 50.

The condensed and unvaporized liquid, which has a greater density than the liquid-vapor mixture rising through conduit 32, is returned to the boiler shell through conduits 11. This liquid is deposited within the boiler shell 12 at the area 38 between the shell and the shroud 20. The shroud 20 directs the liquid to the bottom of the boiler shell 12 where it is vaporized by the heat from fire tubes 16 and return tubes 18.

The fact that each of the return conduits 1.1 are disposed concentrically and in spaced relationship to respective conduits 32, allows the conduits 11 to each have a significantly larger area than would otherwise be possible. This results in less pressure drop through corresponding conduits with enhanced circulation of the liquid passing therethrough. It is also clear from FlG. 2 that this preferred construction of the assembly eliminates the need for field welding and enhances the appearance of the assembly while permitting external insulation thereof to be achieved on the job site easily and efficiently.

It is to be understood however, that the specific arrangement of the conduits 11 and 32 shown in the drawing is not essential to the effective use of the shroud 20, and in some embodiments the conduit 11 may be disposed with its center in spaced relationship to the center of the conduit 32 and with the two conduits completely separate. It is, of course, necessary that the conduit 11 communicate the bottom of the separation chamber 14 with the top of the boiler shell 12.

It is to be understood that other modifications from the specific embodiment herein shown and described may be made without departing from the scope of the invention. For example, the ends of the shroud may be left open, or closed into the shell 12 as required for each specific application. Also, support for the shroud 20 may be alternately achieved from tube baffles such as plate 17 which are customarily included in a fire-tube boiler. Furthennore, while the invention has been described with specific application to fire-tube boilers, it will have application to many kinds of industrial heaters and boilers.

Having thus described the invention, what I claim as new and desired to be secured by Letters Patent is:

l, A boiler assembly comprising:

an elongated, horizontally disposed, transversely circular shell for receiving liquid to be vaporized;

a series of elongated, spaced, relatively large diameter fire tubes extendinglongitudinally of the shell;

a plurality of spaced, elongated gas return tubes of smaller diameter than said fire tubes and extending longitudinally of the shell;

upright baffle means at opposite ends of the shell supporting the fire tubes and said gas return tubes and dividing the shell into an intermediate liquid receiving and vaporizing compartment and hot products of combustion manifold chambers at opposite ends of the shell, the fire tubes and said gas return tubes communicating with a manifold chamber at one end of the shell, the opposite end of the shell being provided with means for communicating the fire tubes with a burner for direct receipt of hot products of combustion therefrom, the gas return tubes communicating with the manifold zone at said opposite end of the shell and there being means for discharging hot products of combustion from the manifold zone at said opposite end of the shell;

a horizontal, semicylindrical shroud carried within said compartment of the shell in spaced relationship from the latter and in partially circumscribing relationship to the fire tubes and said gas return tubes,

said shroud being provided with upright, semicircular end edges in close proximal relationship to respective baffle means defining opposite ends of said compartment, and elongated, spaced bottom margins extending longitudinally of the shroud below a horizontal plane through the axis of the shroud;

an elongated, transversely circular vessel positioned directly above the shell in a position with the axis thereof parallel to the axis of the shell, said vessel extending substantially the full length of the compartment of said shell and provided with a vapor outlet in the upper portion thereof;

a line of individual, upright first conduits intercommunicating said compartment of the shell with the interior of said vessel at a plurality of points along substantially the full length of the compartment, the conduits at opposite ends of the line thereof being positioned in proximal relationship to respective baffle means defining opposite extremities of the compartment; an upright second conduit within and spaced from each of the first conduits, penetrating the shroud and terminating in said vessel for communicating the latter with the compartment of said shell below the shroud; and

baffle means on the uppermost ends of said second conduits for facilitating separation of vapor from liquid whereby a mixture of vapor and liquid produced in said shell is directed upwardly through said second conduits along a plurality of parallel upright paths into the vessel, vapor is separated from the liquid and removed from the vessel via said vapor outlet, and liquid collected in the vessel is returned to the shell via said first conduits for flow to the lower part of the shell along the shroud throughout substantially the entire length of the compartment.

2. A boiler as set forth in claim 1, wherein is provided an elongated, upwardly facing, open-ended, transversely channel-shaped dry-pipe within the vessel in underlying relationship to said vapor outlet, communicating therewith and extending along a substantial part of the longitudinal length of the vessel. 

1. A boiler assembly comprising: an elongated, horizontally disposed, transversely circular shell for receiving liquid to be vaporized; a series of elongated, spaced, relatively large diameter fire tubes extending longitudinally of the shell; a plurality of spaced, elongated gas return tubes of smaller diameter than said fire tubes and extending longitudinally of the shell; upright baffle means at opposite ends of the shell supporting the fire tubes and said gas return tubes and dividing the shell into an intermediate liquid receiving and vaporizing compartment and hot products of combustion manifold chambers at opposite ends of the shell, the fire tubes and said gas return tubes communicating with a manifold chamber at one end of the shell, the opposite end of the shell being provided with means for communicating the fire tubes with a burner for direct receipt of hot products of combustion therefrom, the gas return tubes communicating with the manifold zone at said opposite end of the shell and there Being means for discharging hot products of combustion from the manifold zone at said opposite end of the shell; a horizontal, semicylindrical shroud carried within said compartment of the shell in spaced relationship from the latter and in partially circumscribing relationship to the fire tubes and said gas return tubes, said shroud being provided with upright, semicircular end edges in close proximal relationship to respective baffle means defining opposite ends of said compartment, and elongated, spaced bottom margins extending longitudinally of the shroud below a horizontal plane through the axis of the shroud; an elongated, transversely circular vessel positioned directly above the shell in a position with the axis thereof parallel to the axis of the shell, said vessel extending substantially the full length of the compartment of said shell and provided with a vapor outlet in the upper portion thereof; a line of individual, upright first conduits intercommunicating said compartment of the shell with the interior of said vessel at a plurality of points along substantially the full length of the compartment, the conduits at opposite ends of the line thereof being positioned in proximal relationship to respective baffle means defining opposite extremities of the compartment; an upright second conduit within and spaced from each of the first conduits, penetrating the shroud and terminating in said vessel for communicating the latter with the compartment of said shell below the shroud; and baffle means on the uppermost ends of said second conduits for facilitating separation of vapor from liquid whereby a mixture of vapor and liquid produced in said shell is directed upwardly through said second conduits along a plurality of parallel upright paths into the vessel, vapor is separated from the liquid and removed from the vessel via said vapor outlet, and liquid collected in the vessel is returned to the shell via said first conduits for flow to the lower part of the shell along the shroud throughout substantially the entire length of the compartment.
 2. A boiler as set forth in claim 1, wherein is provided an elongated, upwardly facing, open-ended, transversely channel-shaped dry-pipe within the vessel in underlying relationship to said vapor outlet, communicating therewith and extending along a substantial part of the longitudinal length of the vessel. 